1. Field of the Invention
The present invention relates generally to the electrolytic generation of a halogen, such as chlorine or bromine, for treating algae and bacteria within a water source, such as a swimming pool. More particularly, the present invention relates to an improved system of controlling the production of halogen through control of flow rate to the electrolytic cell and through control over the operation of the electrolytic cell in response to measured parameters in a flow stream to the cell.
2. Description of the Prior Art
The use of halogens, particularly chlorine, to treat water systems such as swimming pools for algae and bacteria has been well known. A common procedure involving the manual introduction of chemicals into the swimming pool, although seemingly simple, has associated problems involving labor and safety issues. This method requires that the water be tested frequently to determine when the chemicals need to be added or if the amount being used is proper. The manual introduction of the chemicals also means that a certain amount of time is required before sufficient dispersion will take place, which results in areas of higher concentrations of chemicals in certain portions of the pool and discomfort for swimmers entering these areas. These methods also require the transportation, storage and handling of often dangerous materials presenting issues of safety and liability for proper care.
Other techniques involve the electrolysis of a brine solution to generate a gaseous form of halogen, such as chlorine gas, which is then collected at the top of a chamber for introduction into the pool water system as disclosed in U.S. Pat. No. 4,693,806 to Tucker and U.S. Pat. No. 5,037,519 to Wiscombe. While these techniques may have reduced the amount of labor involved by eliminating the manual addition of chemicals into the pool and the frequent testing of the water to determine the proper application, concerns over safety remain. These methods require the use of a relatively complicated structure involving a barrier between the anode and cathode sides of the device in order to contain the brine, and to separate the gases which are produced, chlorine and hydrogen in the case of a chlorinator. A safety issue concerns the building up of excess gases in such a device, hydrogen being a highly explosive gas and chlorine gas being poisonous. The use of these systems therefore requires extra care to prevent release or explosion of such gases. These systems are also generally not without labor requirements. The use of the brine solution generally requires that the brine must periodically be replenished as it is depleted. Furthermore, water must be periodically added to maintain the brine in solution.
A further series of techniques involves the electrolytic generation of a halogen, such as chlorine or bromine, by flowing at least a portion of circulating pool water to which a relatively small amount of halogen salt has been added, through the cell to convert the halogen salt into halogen directly in the flow stream. In a chlorinator, for example, dissolved sodium chloride is converted into sodium hypochlorite, as is disclosed in U.S. Pat. No. 4,100,052 to Stillman. Stillman discloses a system which includes a controller for the electrolytic cell, the controller also being connected to the main circulating pump for the pool system. The control system of Stillman is built on a timing system wherein the pump has a cycle of operation and the cell has a shorter cycle contained within the cycle of the pump. An example given is a 12 hour on, 12 hour off cycle for the pump and a 12 minute on, 3 minute off cycle for the cell within the 12 hour on time of the pump.
The control systems of the prior art leave room for improvement in obtaining optimum halogen production for a given cell in a given system. A system that merely controls on/off time of the cell, for example, is not responsive to fluctuations in the flow rate which the circulating pump is presenting to the production cell. These fluctuations in flow rate could result, for example, from obstructions trapped in the filter of the system. Further, it is known in the art, that the production of halogen from an aqueous solution containing a dissolved halogen salt will vary depending on the temperature of the solution as well as the concentration of the halogen salt in the solution.
Therefore, it is an object of the present invention to provide a control system for halogen production in which the flow rate to an electrolytic cell is controlled and in which the operation of the cell is controlled in response to measured parameters including flow rate, water temperature and conductivity.